1. Field of the Invention
The present invention relates to a control apparatus for elevator system which detects an abnormal driving state of a cage to output an emergency stop command signal.
2. DESCRIPTION OF PRIOR ARTS
In usual, a cage of an elevator is driven by a speed pattern signal and a driving direction command signal corresponding to a distance to the floor at a calling under receiving the calling signal.
When the cage is driven to the direction opposite to the calling direction, that is, the opposite direction to the direction of the driving command signal or a command speed pattern is not output even though the driving direction command is output or a braking of a motor is not released even though the driving direction command is not output, there is a possibility to start a cage under a balance of a weight of the cage and a counter-weight is lost. (Such state will be referred to as abnormal driving state). Such state is remarkably dangerous. The cage of the elevator should be stopped by an emergency stop.
FIG. 1 shows a block diagram of an abnormal driving state detecting mechanism in the conventional elevator system.
In FIG. 1, a cage (10) for an elevator (hereinafter referring to as a cage) is held in a hoistway (12) and is suspended by a wire rope (14). The wire rope (14) is hung on a traction sheave (18) connected directly a shaft of a traction motor (16). A counter-weight (20) is bound at the other end of the wire rope (14). A speed tachometer (22) is driven by a timing belt (24) hung on the traction sheave (18) and outputs a cage speed voltage (26) having (-) polarity in the ascending driving of the cage (10) and outputs one having (+) polarity in the descending driving, in proportional to a speed of the cage. A driving direction commanding device (28) receives a calling signal (30) and a cage position signal (32) to output an ascending command signal (28a) or a descending command signal (28b) during the driving. A command speed pattern generator (34) receives an output of the driving direction commanding device (28) to output a command speed voltage (36) having (+) polarity in the output of the ascending command signal (28a) (logical value "1") and one having (-) polarity in the output of the descending command signal (28b) (logical value "1") to a motor driving control circuit (38). The motor driving control circuit (38) inputs a cage speed voltage (26) and a command speed voltage (36) whereby the rotary speed of the traction motor (16) is controlled so as to drive the cage (10) at the speed commanded by the command speed pattern generator (34). An adder (40) adds the cage speed voltage (26) to the command speed voltage (36). An absolute value amplifier (42) always amplifies the output of the adder (40) to (+) voltage. A reference voltage generator (44) generates a predetermined reference voltage (46). A voltage comparator (48) compares the output voltage of the absolute value amplifier (42) with the reference voltage (46) to output when the output voltage of the absolute value amplifier (42) is greater.
During the normal driving state, the polarity of the command speed voltage (36) is opposite to that of the cage speed voltage (26). Accordingly, certain voltage caused by a time lag of the driving system is given in the output of the adder (40). The voltage is amplified to the voltage having (+) polarity by the absolute value amplifier (42). In the reference voltage generator (44), a reference voltage (46) which is greater than a maximum differential voltage between the command speed voltage (36) and the cage speed voltage (26) in the normal driving state, is previously set. Accordingly, an output is not generated from the voltage comparator (48) in the normal driving state.
When the cage is driven to the direction opposite to the output pattern of the command speed pattern generator (34), the polarity of the command speed voltage (36) is the same as that of the cage speed voltage (26). Both voltages are added in the adder (40). The output of the absolute value amplifier (42) is increased over the reference voltage (46) whereby the voltage comparator (48) outputs.
When the cage is started by certain fault, in spite of zero of the output of the command speed pattern generator (34), the cage speed voltage (26) itself is the output of the adder (40). The output of the absolute value amplifier (42) is increased in proportional to the cage speed whereby the voltage comparator (48) outputs at the time over the reference voltage (46).
Thus, the abnormal driving state is detected by detecting the fact that the difference between the command speed voltage (36) and the cage speed voltage (26) being proportional to the practical speed of the cage is increased over a predetermined value in the conventional apparatus. Smaller predetermined value is desirable. However, the predetermined value should be high enough not to detect it in the normal driving state because of fluctuation of the time lag element of the control system in the driving zone. Accordingly, there has been a disadvantage to be difficult detectng the abnormal driving state driving at slow speed as a falling or a rising in the unbalance between the cage and the counter-weight.